The rapid expansion of the world's population coupled with the accelerated technological development of large sectors of the world has produced a dramatic increase in the demand for energy in all forms including fuels and electricity for heating, lighting, transportation and manufacturing processes. The construction of hydroelectric facilities and the development of fossil fuel resources has continued at a rapid rate, but it becomes increasingly evident for a number of reasons that these efforts are inadequate to keep pace with the demands of the growing population.
Until recently, the development of solar energy collectors has been associated for the most part with programs involving military and space applications while only limited attention has been given to broad consumer use. As a result, there is a great potential for improvements in existing collection devices that will result in reduced manufacturing costs and improved thermal efficiencies.
One such device known as a flat plate collector is made of metal and glass with one or more layers of glass laid over a blackened metal plate. Air spaces are provided between the layers of glass, and air or water passes through tubes under the metal plate to remove the collected thermal energy. The layers of glass in cooperation with the blackened metal plate act as a heat trap, letting in the sun's rays but keeping most of the heat from escaping again.
A major disadvantage of the flat plate collector is that it must be very large in order to collect sufficient energy, the large size resulting in part from the fact that except for brief periods during the day its surface is not perpendicular to the rays of the sun.
A second disadvantage is that the known flat plate collector does not permit the concentration of solar energy at a localized point as needed in order to get temperatures high enough for the conversion of water to steam such as is required in certain solar-to-electrical conversion processes.